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March 19th update: I was able to write a C++ program to accomplish the second step (run a program on the VM) but so far only after the VM was up and running. If I try to do it all in one program the second step fails, I assume because the VM is in some sense not ready.
June 11th update: Test program boots the VM, checks for "running state", checks for availability of disk and attempts to locate the particular script it intends to run. Even when all these checks succeed, the running of the script can still fail. However, it succeeds if a sleep of 100 seconds is inserted before attempting to run the script. 60 is not enough. This is not a very satisfactory state of affairs.
Other Interfaces
VirtualBox provides a variety of ways to get at the core functionality. Approximately from least to most grungy:
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